34 lines
654 B
C
34 lines
654 B
C
/* Based on isin_S4 implementation from coranac:
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* http://www.coranac.com/2009/07/sines/
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*
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*/
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#define qN 15
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#define qA 12
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#define B 19900
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#define C 3516
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int hisin(int x) {
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int c, y;
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c= x<<(30-qN); // Semi-circle info into carry.
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x -= 1<<qN; // sine -> cosine calc
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x= x<<(31-qN); // Mask with PI
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x= x>>(31-qN); // Note: SIGNED shift! (to qN)
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x= x*x>>(2*qN-14); // x=x^2 To Q14
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y= B - (x*C>>14); // B - x^2*C
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y= (1<<qA)-(x*y>>16); // A - x^2*(B-x^2*C)
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return c>=0 ? y : -y;
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}
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int hicos(int x) {
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return hisin( x+32768 );
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}
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